1. Field of the Invention
The present invention relates to a process for separating compressed material containing paper fibers including paper or paperboard webs.
2. Discussion of Background Information
The manufacture of paper or paperboard frequently uses waste paper which is supplied in the form of bales. Even native pulp is often initially formed into bales after production. Such bales are generally produced by compressing the material and then tying it with wires or bands, thus, providing a compact form that is relatively easy to transport. For use as new raw material, it is necessary to break up these compressed bales into individual paper webs or pieces again in order to be able to perform the subsequent procedures for processing the material. Even after the binding wires or bands have been removed from compressed bales, in most cases they stay in one piece or in such large pieces that feeding them into equipment, such as a water-operated pulp dissolver, can cause problems. Moreover, in many cases the material delivered is contaminated with foreign materials, e.g., plastic film, that have been compressed into the bale. These plastic films often adhere to the paper material, which poses an obstacle to their early removal.
German Application No. DE 34 39 098 A1 describes a process in which, in a relatively resource-intensive fashion, bales of recycled waste paper are separated, broken up, and cleaned and brought into suspension by subsequently adding water to them in a pulper. Although this process can be viewed as a suitable step for starting the processing of recycled paper, it has not been generally adopted on account of its high cost.
Machines are already known with which a process of the type generally described above could be performed. These are sturdy coarse chopping or grinding machines, e.g., shredders, that are specifically intended to pre-grind coarse material, e.g., scrap or rocky material, so that it can subsequently further processed or sorted. The use of a shredder in a process of the type generally described above would require a very large machine with a correspondingly high price on account of the size of the bales or bale fragments. Thus, the disadvantages of such a device would include not only its cost and the space required, but also high power consumption. In addition, the operation of such a machine is very harsh and causes a considerable amount of noise.
Another possibility would be the use of a screw extruder or another type of open screw conveyor with at least two conveyor screws. However, machines of this type are also very expensive and have a high power consumption. Moreover, it is necessary to take into account that these machines can also at least partially crush the compressed pulp rather than separate it.